JP3103601B2 - Laser-imageable tuned optical resonator thin film and printing plate incorporating the same - Google Patents

Abstract

A laser imageable tuned optical cavity thin film for use with a laser producing laser radiation at a laser wavelength comprising a flexible sheet of plastic having first and second surfaces serving as a film substrate. A thin film stack is disposed on the first surface of the film substrate and comprises a first vacuum-deposited metal layer carried by the first surface. It is also comprised of a dielectric layer deposited on the first metal layer. A second semi-opaque metal layer is vacuum deposited onto the dielectric layer. The thin film stack is tuned to provide maximum absorption at the laser wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser imageable tuned optical cavity (Optical Cavity) thin film and a printing plate incorporating the same, wherein the printing plate has a writing characteristic using digitized laser radiation. Improved.

The traditional printing method of offset printing is undergoing rapid technological change. That change began when desktop publishing software became commonly used for the layout of graphics in print jobs and replaced camera-pasted pages. Once printers began to receive most of their work in the form of digital data instead of camera-ready works of art, they began to purchase equipment that could use digital information as well . This new device has helped increase the speed and efficiency of the entire printing process. The new equipment also significantly reduced the amount of chemical solution consumed in the printing industry by eliminating the need for developing photographic films or photopolymers. The first digital device purchase was a proofing system, which allowed customers to quickly censor digitally created hard copy swatches before the final printing phase. Even though digital proofing is still used, it is becoming increasingly common to calibrate directly on computer screens and then to the final printout produced by digitally produced printing plates. ing.

Current laser-imaged printing plate technology is limited by the laser sensitivity of currently available materials. It is common practice to image the printing plate directly on a printing press or in a flat-plate scanner. In any case, 400 m
A laser fluence of J / cm ² or more is required. Due to imperfections in the surface of the plate and the surface on which it is mounted, a change in the depth of focus occurs. To overcome these changes, there is a need to improve the operating range of the plate imaging system. In co-pending application Ser. No. 08 / 436,119, filed May 8, 1995, a laser-imaged direct-write film and a printing member incorporating the same are disclosed, comprising titanium, zirconium, aluminum, It incorporates a vacuum deposited laser ablative coating composed of a single layer formed from a material selected from the group consisting of hafnium and their alloys. Even though the aforementioned films and printing members have excellent properties, there is still a need to improve the absorbing properties of the aforementioned films and printing members.

In general, it is an object of the present invention to provide a tuned optical resonator thin film and a printing member incorporating the same.
They have improved sensitivity to infrared laser beams.

Another object of the present invention is to provide a thin film and printing plate that has an increased practical depth of focus and maintains a sharp image throughout the printing plate even with changes in the distance between the laser and the image. An object of the present invention is to provide a thin film having characteristics and a printing plate incorporating the same.

Another object of the present invention is to provide a thin film and a printing plate having the above characteristics, which minimize the effect of a change in the thickness of the adhesive in the thin film and the printing plate to increase the laser sensitivity of the laser absorbing layer. It is to be.

It is an object of the present invention to provide thin films and printing plates that are prepared to maximize absorption at the laser wavelength that is ablating.

Another object of the present invention is to provide a thin film and a printing member having the above properties that can be easily manufactured.

Further objects and features of the present invention will become apparent from the following description in which preferred embodiments are set forth in detail in conjunction with the accompanying drawings.

FIG. 1 is a cross-sectional view of a thin film incorporating the present invention showing a thin film stack on a polymer substrate.

FIG. 2 is a cross-sectional view of the printing plate incorporating the present invention with the prepared optical resonator laser ablation film incorporated therein shown in FIG.

FIG. 3 is a cross-sectional view of another embodiment of a printing plate incorporating the present invention.

FIG. 4 is a graph showing the optical performance of a single metal layer made of titanium with its thickness adapted for maximum absorption at the wavelength of the infrared diode laser.

FIG. 5 is a graph showing the optical performance of the film shown in FIG.

FIG. 6 is a cross-sectional view of another printing plate incorporating the present invention.

Generally, the prepared laser-imageable optical resonator thin film is for use with a laser that generates laser radiation, and the first serves as a substrate.
And a flexible sheet of plastic having a second surface. The prepared optical resonator thin film stack is disposed on a first surface of a substrate. The thin film stack includes a first vacuum deposited metal layer held on a first surface of a substrate. A dielectric layer is deposited over the first metal layer at an odd multiple of a quarter wavelength at the design wavelength of the laser. Second
A vacuum deposited metal layer is deposited over the dielectric layer. An organic or silicone top coat covers the second metal layer. The thin film stack is tuned by various layer thickness designs for maximum absorption at the laser wavelength.

More specifically, as shown in FIG. 1 of the drawings, the laser-imageable prepared optical resonator thin film 11 is a flexible sheet or film substrate 12 formed of organic plastic.
Having. The sheet or film substrate has first and second surfaces 13 and 14, and has a thickness of 0.2 to 10 mils, and preferably has a thickness of 7 mils. The substrate is formed of a suitable material such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), which is transparent or filled with barium sulfate,
Or a flexible metal substrate such as aluminum. In the latter case, an evaporative layer of PET or other suitable polymer can be deposited to mimic the polyester substrate shown in the first example. This structure can eliminate the need for lamination. MYLAR, ICI 442, Hoechst (Hoe) supplied by Dupont
scht) 3930, ICI 329, and ICI Kaladex (Kal
adex).

The thin film stack can be held on the first surface 13 to provide a leaky or leak-free prepared optical resonator.

When a leaky optical resonator is provided, stack 16 has a first partially transmissive reflective metal layer 17 vacuum deposited on a first surface. The first metal layer may be formed of a bright metal, such as aluminum, or a gray metal, such as chromium, nickel, or titanium, which acts as both an absorber and a reflector in the design of the present invention. Things. The first metal layer 17 is 65 to 500
金属 is deposited in a thickness in the range of Å, the metal layer having an optimum thickness selected to give the greatest benefit considering heat capacity, thermal conductivity and absorption, and partially It should be absorbent, partially transmissive, and partially reflective. When titanium is used for the layer, the optimal thickness of the first metal layer is 220 °.

When a leak-free resonator is desired for the thin film stack 16, an opaque reflective metal layer of aluminum, nickel, titanium or chromium is deposited on the first surface at a thickness in the range of 500-2000 ° and the first A metal layer 17 is provided.

The dielectric 18 has a thickness of between one third and one fifth of the optical wavelength at the laser wavelength, and preferably one quarter of the optical wavelength, of the first metal layer. Attached on top.
The material for the dielectric layer 18 is magnesium fluoride, aluminum oxide, silicon dioxide, high index
Oxides, metal fluorides, metal sulfides, thermally evaporating polymers and vacuum deposited polymers,
It can be selected from polymers that can be cured in vacuo by in situ polymerization, such as electron beam or radiation techniques, and polymers deposited by chemical vapor deposition. However, magnesium fluoride is the preferred material, and evaporative polymers are even more preferred.

A second metal layer 19 having an optimum thickness of 65 ° was vacuum deposited on the dielectric layer 18 in a thickness ranging from 25 ° to 100 °. The metal selected for the second metal layer 19 is the same metal as the first metal layer 17.

Organic topcoat 21 is deposited on second metal layer 19 at a thickness of 0.5 to 4 micrometers and is designed to be used with silicone or fountain solution for waterless lithography. , But is not limited thereto.

In the preparation of the laser ablation film 11, a roll coater can be used, where a film substrate is used.
12 is transported by rollers and passes through a vacuum chamber in a roll coater. Metal layers 17 and 19 and dielectric layers
The 18 and top organic layers 21 can be deposited sequentially in the desired order in a single pass. Alternatively, the three layers can be deposited in multiple passes through a roll coater without breaking the vacuum.

Alternatively, the film substrate 12 carrying the layers 17, 18 and 19 can be removed from the roll coater and the organic topcoat can then be applied at atmospheric pressure in a conventional wet process. This can be done in the same facility or a separate facility for the rolled film substrate 12 in a roll coating operation. Thus, the thin organic coating 21 can be applied in a manner well known to those skilled in the wet coating process. Thereafter, the wet coating can be cured by ultraviolet light or thermal heating until the topcoat 21 adheres to the top metal layer 19 and is completely cured.

In connection with the printing ink (s) used with the laser-imageable film of the present invention, the topcoat is made to have hydrophilic or hydrophobic and oleophilic or oleophobic properties. 21 is prepared. By way of example, the organic coating may take the form of a lipophilic material such as a silicone polymer that repels the ink. Alternatively, the organic coating may be in the form of a hydrophilic material such as polyvinyl alcohol that attracts water. The organic top coat 21 may also be characterized as a coating film having an affinity different from the affinity of the thin film substrate 12 for at least one printing liquid selected from the group consisting of ink and an anti-adhesion liquid for ink. it can.

After the cavity laser ablation film 11 has been prepared by the method described above, it is attached to a supporting substrate or plate 26 having an upper or first surface and is directly laser-imageable as shown in FIG. A writing printing member 31 may be formed. Film 11 is adhered to a base structure or plate 26, which is typically made of aluminum of a thickness such that it is flexible, ie, 5-12 mils, and film 11 is an adhesive (not shown). The adhesive can also be mounted on the cylinder by any suitable means, such as on the surface 14 or on the surface 27 so that the adhesive is dimensionally stable on the surface 27 of the base structure or plate 26. It can be fixed in form and laminated. The base structure or plate 26 is preferably dimensionally stable,
2 between typical operating temperatures ranging from 50 degrees Fahrenheit to 100 degrees Fahrenheit
Excursion exceeding 5 mils over a length of 0 inches (excur
sion).

Another embodiment of a printing plate incorporating the present invention is shown in FIG. 3, which eliminates the need for lamination. The printing plate 36 in FIG. 3 has a preferred thickness of 5-12 mils and comprises a flexible metal substrate 37 of a suitable metal such as aluminum having a surface 38. Polymer dielectric layer 39 is provided on surface 38 in a thickness of 0.25 to 2 mils. This layer 39 is made of PE
T may be an evaporable layer, and this layer 39
And 2 are provided to mimic the function of the substrate 12 in the embodiment shown. This layer 39 has a thin film stack 41 similar or identical to the thin film stack 16 described above deposited thereon.

The composite printing plates or members 11, 31, and 36 as shown in FIGS. 1, 2 and 3 are then utilized and loaded directly into the printing press to form the image or by an infrared diode laser. It can be loaded into an image setting machine that forms and forms an image on the laser ablation film 11. Image formation occurs due to the ablation mechanism. Upon exposure to the infrared laser beam, decomposition or gasification of the first surface 13 of the organic film substrate 12 occurs.
3) causes the decomposition of the interface between the substrate 12 and the first metal layer 17 in FIG. 2 or between the layer 39 and the metal layer 17 in FIG. Wiping the plate with a solvent such as isopropyl alcohol, from the imaged area of the plate, layer 17,
Allows removal of 18, 19 and 21 remaining parts.

In a leaky resonator absorption system, the first metal layer 17 is partially transparent. The polymer layer 12 is a dielectric layer from the top metal layer 19 that absorbs laser energy.
Heat is transferred through 18 and the first metal layer 17, and in layer 17, the heat transfer is combined with energy directly absorbed by layer 17 and heated to bring polymer layer 12 to its decomposition temperature. Its decomposition temperature, such as 265 ° C (538 Kelvin) for PET,
18 and 19 below the melting or vaporizing temperature. In a leak-free cavity absorption system, the majority of the laser light is reflected from the first metal layer 17, and
The dielectric used at 18 is a polymer. The formation of the image is similar to that described above, except that decomposition and gasification occur in the dielectric layer 18 to remove the top metal layer 19.
Occurs due to ablation mechanisms similar to leaky resonators. If the polymer dielectric layer is oleophilic and if some polymer layer is left after the top metal layer 19 has been removed, the plate is the entire stack or layer 17,
It will work in a similar fashion as 18 and 19 have been removed. If polymer dielectric layer 18 is the top metal layer
If removed with 19 to expose the underlying reflective layer, then the reflective layer 17 can act as a hydrophilic layer to attract the wetting solution, and the top organic layer 21 can be the parent layer. Can act as an oily layer. It is advantageous that the layer absorbing the laser does not melt or vaporize. Because such a gas phase transition consumes laser energy without a corresponding increase in temperature, which reduces ablation sensitivity. This is a very important consideration as the laser diodes typically used in such applications operate at low power output.

Laser ablation film 11 has improved laser ablation sensitivity over a single metal or carbonate matrix absorbing layer, and it has a high absorption at the laser wavelength. This absorptivity is determined by the dielectric layer 18
By properly selecting the thickness of the metal layers 17 and 19, and by adjusting the thin film stack 16 for minimum reflection and maximum absorption for the laser frequency,
Achieved.

FIG. 4 is a graph showing the calculated absorption obtained from a single metal layer made of 210 ° titanium.

FIG. 5 shows the optical performance of an improved specific laser ablation film 11. The particular film embodies the present invention, the first metal layer 17, formed of 220 ° nickel, the dielectric layer 18 formed of 1812 magnesium fluoride and the second metal layer formed of 65 ° nickel. It shows the high absorption obtained with the above-described resonator laser ablation film made with metal layer 19 and having an absorption of more than 90% from 800 to 1100 nm.

FIG. 6 is a sectional view of another embodiment of a printing plate embodying the present invention. The adhesive used to laminate the laminar structure 11 to the base support structure 26 in FIG. 2 is removed along with the PET substrate and the metal layer 17, and then the layers 18, 19 and 21 are placed on the base support structure 26. Directly adhere to Alternatively, as shown in FIG. 6, the printing plate 46 is, for example, 5-12
It is made of a flexible metal substrate 47, such as aluminum, having a suitable thickness, such as mil. Substrate 47 is the surface
And having on its surface an evaporable polymer dielectric layer 49 with a thickness not limited to one-third and one-fifth of the optical wavelength at the laser wavelength as in the previous embodiment of the invention. Is attached. However, it should be deposited with a thickness in the range of 50 to 400 mm. The dielectric layer 49 is covered by an absorbing metal layer 51, which is 25 to 100 mm thick. A top coat or layer 52 overlies the metal layer 51 to complete the thin film coating of the printing plate 46. Layer 52 is formed of an organic or silicone material and is deposited in a vacuum or by a conventional chemical deposition process.
Thus, this layer 52 is useful in the methods described above as a lipophilic or hydrophilic layer.

From the foregoing, there is provided a laser-imageable direct-write cavity laser ablation film having a very low ablation threshold by adjusting the ablative coating to the frequency of the laser utilized. .

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Bradley, Richard, A. United States 95401 Santa Rosa Lawrence Way, California 1436 (72) Inventor Fischer, Shari, Pey. United States 95401 Santa Rosa Halliard Drive, California 1174 (72) Inventor Phillips, Roger, W. United States 95405 Santa Rosa Jacqueline Drive, California 466 (58) Field surveyed (Int. Cl. ⁷ , DB name) B41N 1/14 B32B 7/02 103

Claims (16)

(57) [Claims] 1. A tuned optical resonator thin film for use with a laser that emits laser radiation at a laser wavelength, wherein said thin film is provided as a film substrate in a first and second tuned optical resonator. A first vacuum comprising a flexible sheet of organic plastic having a surface and a thin film optical resonator stack disposed on the first surface of the film substrate, wherein the thin film stack is held on the first surface; A deposited metal layer, a dielectric layer deposited on said first vacuum deposited metal layer, and a second vacuum deposited semi-opaque metal layer deposited on said dielectric layer; Wherein the thin film stack is conditioned by the thickness of the first vacuum deposited metal layer, the thickness of the dielectric layer, and the thickness of the second vacuum deposited translucent metal layer, Thin film and providing a maximum absorption at the laser wavelength. 2. The thin film according to claim 1, wherein said dielectric layer has a thickness which is an odd multiple of a quarter wavelength of said laser wavelength. 3. The tuned optical resonator is leaky, and the first vacuum deposited metal layer is partially absorbent, partially transparent, and partially reflective. The thin film according to claim 1, wherein the thin film has a property. 4. The tuned optical resonator is leak-free, and the first vacuum-deposited metal layer is opaque;
The thin film according to claim 1, wherein the thin film is reflective. 5. The thin film according to claim 1, wherein the thin film is combined with an organic top coat held in the thin film stack. 6. The first and second vacuum-deposited metal layers are formed of a metal selected from aluminum, chromium, nickel, titanium, zirconium, hafnium, or an alloy thereof. The thin film according to claim 1. 7. The method of claim 1, wherein said first vacuum deposited metal layer comprises
2. The thin film according to claim 1, having a thickness in the range of 2000 [deg.]. 8. The method according to claim 7, wherein said second vacuum deposited metal layer comprises
A thin film according to claim 7, having a thickness in the range of 100 °. 9. The method of claim 1, wherein the dielectric layer is magnesium fluoride, aluminum oxide, silicon dioxide, high index oxide, metal fluoride, metal sulfide, thermally evaporated polymer, vacuum deposited polymer, 2. A polymer that can be cured in a vacuum by electron beam or radiation techniques and / or is deposited by chemical vapor deposition.
2. The thin film according to 1. 10. The thin film according to claim 1, wherein the thickness of the dielectric layer is between one third of the optical wavelength and one fifth of the optical wavelength at the laser wavelength. . 11. The thin film according to claim 4, wherein said dielectric layer is made of a polymer material. 12. The thin film according to claim 1, wherein the flexible sheet made of organic plastic is a white film filled with barium sulfate. 13. The thin film according to claim 1, wherein said film substrate has a thickness in the range of 0.2 to 10 mil. 14. A lithographic laser-imageable printing plate for use with a laser that generates laser energy at a laser wavelength, said printing plate having a first surface and 5 to 20 mils. A base support substrate having a thickness of, and an ablation film laminated on the first surface, wherein the laser ablation film has first and second surfaces and is provided as a film substrate. A flexible sheet and a thin film optical resonator stack disposed on a first surface of the film substrate, wherein the thin film stack comprises:
A first vacuum-deposited metal layer held on a first surface of the film substrate, a dielectric layer deposited on the first vacuum-deposited metal layer, and a dielectric layer deposited on the dielectric layer; A second vacuum-deposited translucent metal layer, wherein the thin-film stack comprises a first vacuum-deposited metal layer thickness, a dielectric layer thickness, and a second vacuum-deposited metal layer. A printing plate characterized by providing maximum absorption at the laser wavelength, adjusted by the thickness of the applied translucent metal layer. 15. The method according to claim 15, wherein said dielectric layer has a thickness of 4 at a laser wavelength.
Characterized by having a thickness of an odd multiple of one-half wavelength,
15. The printing plate according to claim 14. 16. The method according to claim 14, wherein the first surface of the base support substrate acts as an opaque metal layer of the thin film stack to provide a leak-free printing plate.
Printing plate described in.